Automation systems are widely used in manufacturing processes for productivity improvement. A typical automation system consists of a programmable logic controller (PLC), sensors and actuators, input/output (I/O) related connections either via fieldbus or direct wiring, and control logic which runs on the controller. Based on the state of sensor input, a controller commands the system (the actuators) to perform specific actions as designed by an engineer and prescribed in the control logic codes. As the control logic code is a type of software, initial bugs and errors are typical upon implementation, as is often the case with computer software. With advancement of computational technology, control logic can be tested and verified using math-based methods or an emulated system. However, the hardware and installation-related issues of the automation system cannot be tested using the math-based method or an emulated system alone. Therefore, field testing of the automation system is always required to verify that the system behaves as expected (i.e., as designed) by the engineer.
Traditionally, there are two types of field tests for validating a manufacturing automation system. These field tests may be often referred as “dry run” mode and “trial run” mode. In a “dry run” field test mode, the works-in-process (WIPs) are not present. The WIPs are also referred to herein as the work pieces, and are the physical entities that are manufactured or processed by the manufacturing automation system. For example, an automated vehicle assembly line undergoes a dry run field test mode without any vehicle components. In order to dry run a manufacturing automation system, any portion of the control logic that involves an input check of sensors that sense the presence and absence of the WIP has to be bypassed so that the automation system will run properly according to the control logic, as there is no physical WIP present. To disable the sensor input checking, special care needs to be taken during the control logic programming stage. A special “dry run” mode may be inserted into the control logic, or the sensor input could be manually provided through a specially programmed human-machine interface (HMI). The addition of the specific “dry-run” mode into the control logic increases the complexity of the code as well as increases engineering time. Furthermore, the main drawback of this type of “dry run” practice is that it may miss any potential faults in the control logic which depend on the validity of sensor input checking. Although the missed faults in the control logic can be discovered during the real “trial run” with physical components present and sensor input enabled, this may delay the launch of regular production using the automated system.